JPH0145778B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention involves transmitting a training signal from an opposing multi-value transmission device prior to data transmission, and converting the training signal from analog to digital by the multi-value transmission device that receives the training signal. This invention relates to a training method that can enlarge the pull-in range of an automatic equalizer and ensure equalization by using a multi-value transmission system that sets tap coefficients of the automatic equalizer.

(b) Background of the technology In the case of multilevel transmission, the level interval is generally narrow, so prior to data transmission, a training signal is transmitted, and the tap coefficients of the automatic equalizer on the receiving side are determined. In this case, the tap coefficients are slightly changed based on the predetermined tap coefficients so that automatic equalization can be performed smoothly and quickly.

(c) Prior art and problems As conventional training methods, one method receives the training signal and determines the tap coefficient of the automatic equalizer without comparing it with the same pattern signal as the training signal, and the other method uses the training signal to determine the tap coefficient of the automatic equalizer. There is a method to determine tap coefficients for an automatic equalizer by comparing them. In either case, a binary random pattern with maximum positive and negative values is generally used as the training signal. Therefore, in the former case, when the transmission line distortion becomes large, the automatic equalizer estimates the polarity signal and error signal incorrectly, resulting in a small pull-in range and slow pull-in.In the latter case, the polarity signal and error signal are There is no error in signal estimation, but when the pulse interval of the training signal becomes narrower, one pulse affects other pulses, causing distortion and making it difficult to synchronize with the matching pattern, making it difficult to synchronize with the matching pattern. There is a drawback that the automatic equalizer may eventually diverge.

(d) Object of the Invention In view of the above-mentioned drawbacks, the object of the present invention is to provide a method for comparing the matching pattern with the training pattern so that the matching pattern can be completely synchronized with the training pattern, and to adjust the pulse interval of the training signal to an automatic equalizer. To provide a training method that can enlarge the pull-in range of an automatic equalizer by setting the interval at which distortion converges longer than the tap length.

(e) Structure of the Invention In order to achieve the above object, the present invention sets a training signal pattern such that, after n symbol clocks at which distortion due to the transmission path converges, pulses of the maximum positive multilevel level are transmitted for one symbol clock. send out, next
After 2n symbol clocks, a pulse with the maximum negative multilevel level is sent for 1 symbol clock, and then the next n
During the symbol clock and during the previous n and 2n symbol clock periods, the repeating signal is set to 0 level if the multilevel number is an odd number, and to a DC balanced level at the minimum positive and negative multilevel level if the multilevel number is even. year,
At the output of the analog-to-digital converter on the transmitting side,
The average value of the maximum value and the second maximum value obtained by sampling the training signal is set as a threshold voltage,
It has a threshold voltage circuit that outputs an output when the training signal exceeds the threshold voltage, and this output starts a pattern generator that generates the same pattern as the training signal starting from the maximum positive multilevel level of the training signal. This training method is characterized in that the automatic equalizer compares the output of this pattern generator and sets tap coefficients.

(f) Embodiment of the invention An embodiment of the invention will be described below with reference to the drawings.

FIG. 1 shows a training signal pattern according to an embodiment of the present invention, and A shows a case where the number of multi-values is 8 (even number), and B shows a case where the number of multi-values is 7 values (odd number). FIG. 2 is a block diagram showing the circuit configuration of a main part of an embodiment of the present invention, and FIG. 3 shows a waveform when the training signal shown in FIG. 1A passes through a transmission line.

In the figure, 1 is a training signal pattern generator on the transmitting side, 2 is a low-frequency wave generator, 3 is an amplifier, 4 is an analog-to-digital converter (hereinafter referred to as an A/D converter), and 5 is a threshold voltage circuit. 6 is a pattern generator, 7 is an automatic equalizer, and 8 is a transmission path.

As shown in FIGS. 1A and 1B, one period of the repetition pattern of the training signal used in the case of the present invention is n symbol clocks, which is the time required for the distortion caused by the transmission path of the pulse of the maximum multilevel one symbol clock to converge. When set, a pulse with the maximum positive multilevel level is sent out for one symbol clock after n symbol clocks, and a pulse with the negative maximum multilevel level is sent out for one symbol clock after the next 2n symbol clocks. However, during the next n symbol clock and between the previous n and 2n symbol clocks, if the multi-value number is an odd number, the level is 0, and if it is an even number, the DC balance is maintained. For example, in the case of 8 values, As shown in FIG. 1A, the level is -1/2 between the first n symbol clock and the next n symbol clock, and the level is + between the next n symbol clock and the next n symbol clock.
Set to 1/2 level.

In the multilevel transmission device on the transmitting side, the pattern generator 1 generates the above-mentioned pattern as a training signal, and the signal is transmitted through the low frequency filter 2 transmission line 8 to the multilevel transmission device on the receiving side. In the multilevel transmission device on the receiving side, the analog signal of the received training signal is sampled by an A/D converter through an amplifier 3 and converted into a digital signal, which is input to an automatic equalizer 7 and a threshold voltage circuit 5. In the threshold voltage circuit 5, the average value of the maximum value of one cycle and the second maximum value of the training signal obtained by sampling is set as a threshold voltage, and when the training signal exceeds this threshold voltage, the output is sent to the pattern generator 6. . pattern generator 6
starts with this output, but the pulses emitted by this pattern generator 6 start from the maximum positive multilevel level of A, as explained in FIG. 1B,
Thereafter, digital signals having the same pattern as in FIG. 1B are generated. The output of this pattern generator 6 and the output of the A/D converter 4 are input to an automatic equalizer 7, and the automatic equalizer 7 compares the output of the pattern generator 6 and converts the training signal into this pattern generator. The tap coefficient is set to match the pattern of the generator 6. When the training signal of the pattern shown in FIG. 1A is sent through the transmission line 8, it is distorted in the transmission line 8, and as shown in FIG. At the falling point, it becomes a hunting waveform as shown in the figure. However, in the pattern used in the present invention, these hunting distortions are spaced apart so as not to affect other pulses, so the threshold voltage circuit 5 can reliably capture the pulse with the maximum positive multilevel level that exceeds the threshold voltage. . The threshold voltage is determined by a in Figure 3, i.e. the average value of the maximum value and the second maximum value during the first cycle of the training signal, i.e. the value obtained by sampling the pulses of the maximum positive multilevel level. It is determined by the average value of the maximum value and the second maximum value, and there is no mistake even if the hunting distortion is large in finding the maximum positive multi-value level of the period b in FIG.

Therefore, the timing of the training signal and the output of the pattern generator 6 perfectly match, and
Since one pulse is not affected by distortion of other pulses, the automatic equalizer 7 has a wide pull-in range and shortens the pull-in time. Furthermore, since a DC-balanced pattern is sent, even if the phase of the carrier in the demodulator (not shown) of the multi-value transmission device is shifted by 180 degrees and the polarity of the received signal is reversed, the operation will continue in exactly the same way. It will be done.

(g) Effects of the invention As explained in detail above, according to the present invention,
The automatic equalizer can reliably set tap coefficients, and has the effect of widening the training signal pull-in range and shortening the pull-in time.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the training signal pattern of an embodiment of the present invention, FIG. 2 is a block diagram showing the circuit configuration of the main part of the embodiment of the present invention, and FIG. 3 is a diagram showing the training signal of FIG. 1 transmitted. This is a time chart of the waveform when passing through the road. In the figure, 1 is a pattern generator, 2 is a low frequency generator, and 3
is an amplifier, 4 is an analog-to-digital converter, and 5 is an amplifier.
is a threshold voltage circuit, 6 is a pattern generator, and 7 is a threshold voltage circuit.
indicates an automatic equalizer, and 8 indicates a transmission path.

Claims (1)

[Claims] 1. In a multi-value transmission system in which a training signal is transmitted from an opposing multi-value transmission device prior to data transmission, the multi-value transmission device that receives the training signal performs analog-to-digital conversion and sets tap coefficients for an automatic equalizer. The training signal pattern is such that a pulse with the maximum positive multilevel level is sent out for one symbol clock after n symbol clocks when the distortion due to the transmission path converges, and a pulse with the maximum negative multilevel level is sent out after the next 2n symbol clocks. A pulse is sent for one symbol clock, and during the next n symbol clock and the previous n, 2n symbol clock periods, the pulse is a repetitive signal with a DC balanced level, and the receiving side performs analog-to-digital conversion. The output of the device has a threshold voltage circuit that sets the average value of the maximum value and the second maximum value obtained by sampling the training signal as a threshold voltage, and outputs an output when the training signal exceeds the threshold voltage, This output starts a pattern generator that generates the same pattern as the above training signal starting from the maximum positive multilevel level of the training signal, and the automatic equalizer collates the output of this pattern generator and taps it. A training method characterized by setting coefficients.